Concept:The basic unit of Igbo pre-colonial political organisation is the smallest social group around which larger structures are built.Explanation:In pre-colonial Igbo society, the family served as the foundation of political life.Larger organisations such as age-grades and village councils grew from family units.The family head represented the unit in community decisions, making the family the basic political building block.Therefore, the correct answer is the family, not the ala, age-grade, or village council.Answer:B. family